CT Perfusion Techniques and Applications in Stroke and Cancer

Lee, Ting‐Yim; Yang, Dae-Myoung; Li, Fiona; Marants, Raanan

doi:10.1007/978-3-030-26957-9_19

Cited by 9 publications

(14 citation statements)

References 56 publications

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“…17 We compared CTP stroke lesion thresholds for three deconvolution algorithms: (1) Fourier Transform-based deconvolution, 19 (2) model-based deconvolution with a plug flow model of contrast transport, 20,21 and (3) model-based deconvolution with a Johnson-Wilson-Lee (JWL) model of contrast transport. 22 The first two were implemented in-house as representative model-independent and model-dependent deconvolution methods. Of note, the model-independent deconvolution algorithm has been described in detail in a previous study 19 and was the algorithm incorporated into clinically-validated RAPID CTP software, so its CTP lesion thresholds (ischemic core: CBF<30%; penumbra: Tmax>6 s) were selected as the reference on which the other two methods’ thresholds were calibrated.…”

Section: Methodsmentioning

confidence: 99%

“…While the implementation details of the CTP4D algorithm is unavailable, the IRF of the JWL model of contrast transport is: 22 where W is the minimum transit time of contrast through the vasculature, E is the fraction of contrast with transit time > W , and k is a decay rate constant related to the heterogeneity of vascular transit time. Compared to the plug flow model, which assumes uniform transit time of contrast through vasculature, the JWL model appends an exponential decay following the boxcar IRF to account for heterogeneity in contrast transit time.…”

Section: Methodsmentioning

confidence: 99%

“…MTT was the area underneath the IRF and Tmax was defined as Tmax = T0 + 0.5MTT. 16,22 Digital Perfusion Phantom-based Threshold Calibration…”

Section: Model-dependent Deconvolutionmentioning

confidence: 99%

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CT perfusion stroke lesion threshold calibration between deconvolution algorithms

Chung

Sarno

Lee

2022

Preprint

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Objective: CTP is an important diagnostic tool in managing patients with acute ischemic stroke, but challenges persist in the reliability of stroke lesion volumes determined with different software. We investigated a systematic method to calibrate CTP lesion thresholds between deconvolution algorithms using a digital perfusion phantom. Approach: The accuracy of one model-independent and two model-based deconvolution algorithms in estimating ground truth cerebral blood flow (CBF) and Tmax in the phantom was quantified. Reference thresholds for ischemic core and penumbra were model-independent CBF<30% and Tmax>6 s, respectively, which is the current clinical standard. The equivalent model-based CBF and Tmax thresholds were determined by comparing linear regressions of phantom ground truth and deconvolution-estimated perfusion between algorithms. Calibrated thresholds were then validated in 63 patients with large vessel stroke by comparing admission CTP ischemic core and <3-hour diffusion-weighted imaging (DWI) lesion volume by Bland-Altman analysis. Agreement in target mismatch (core < 70 ml, penumbra ≥ 15 ml, mismatch ratio ≥ 1.8) determined by the three methods was assessed by Cohen's kappa (κ) and concordance. Main Results: The calibrated thresholds were CBF<15% and Tmax>6 s for both model-based methods. DWI minus CTP lesion mean volume differences (95% limits of agreement) were +16.2 (-30.9 to 63.3) ml, +10.9 (-32.9 to 54.7) ml, and +13.8 (-48.1 to 75.7) ml for model-independent and the two calibrated model-based approaches, respectively. Agreement in mismatch profiles with the two model-based deconvolution methods versus model-independent assessment was κ = 0.87 (95% confidence interval [CI]: 0.72 to 1.00) and κ = 0.86 (95% CI: 0.70 to 1.00), and both achieved 95% concordance. Significance: We reported a systematic method of calibrating perfusion thresholds between deconvolution algorithms based on their quantitative accuracy. This may harmonize ischemic lesion volumes determined by different CTP software.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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CT perfusion stroke lesion threshold calibration between deconvolution algorithms

Chung

Sarno

Lee

2022

Preprint

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“…Maps were calculated by deconvolving the arterial input TDCs from the brain tissue TDCs from 3 × 3 pixel blocks of CT source images with use of the Johnson-Wilson-Lee model to estimate cerebral blood flow, cerebral blood volume, mean transit time, and PS product. 24 BBB permeability should be close to zero, and a recent study has shown that its standard deviation is 0.24 mL/min/100 g. 25 For quantitative assessment, the parametric maps were analyzed by the same operator (F.S.) using custom software (Interactive Display Language v6.1; Research Systems, Boulder, CO).…”

Section: Methodsmentioning

confidence: 99%

Blood–brain barrier permeability in survivors of immune-mediated thrombotic thrombocytopenic purpura: a pilot study

et al. 2021

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Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening disorder of systemic microthrombosis and organ ischemia. The etiology of chronic cerebrovascular outcomes in iTTP survivors is largely unknown. In this pilot study, we measured blood-brain barrier (BBB) permeability in iTTP patients at the start of remission and 6 months later. This prospective pilot study included 7 adult patients with incident iTTP. Eligibility criteria included ADAMTS13 activity <10% and detectable inhibitor at diagnosis. Patients were recruited from London Health Sciences Centre in Canada (2017-2019) within 3 days of hospital admission and followed for 6 months after remission (defined as normalization of platelet count and lactate dehydrogenase with no clinical signs or symptoms of microvascular injury for more than 30 days after the last plasma exchange). All patients had cerebral CT perfusion scans with BBB permeability surface product measurements. Patients (5 women, 2 men) had a mean age of 48 years (range 21-77). At diagnosis, patients had a mean platelet count of 22 (standard deviation [SD] 25) x109/L. At the start of remission, mean BBB permeability surface product was 0.91 (0.30) mL/min/100g. Six months later, the mean permeability surface product was 0.56 (0.22) mL/min/100g, with mean difference: -0.312 mL/min/100g (95% confidence interval: -0.4729 to -0.1510; p=0.0032). In this pilot study of iTTP patients, pathologically increased BBB permeability was evident and, though there was some improvement, this persisted 6 months after remission. Future work will explore the chronicity of these findings and their clinical implications.

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“…Initial structures were built in PQSMOL. The initial geometry optimizations were carried out using density functional theory (DFT) and the B3LYP functional [57][58][59][60] using, successively, the 6-31G and the 6-31G+(d) basis set, as implemented in PQSMol. 61 Frequency calculations in PQSMOL were performed on all n=1.5 optimized structures to ensure stable minima were obtained.…”

Section: Epr Spectroscopymentioning

confidence: 99%

Polaron and Exciton Delocalization in Oligomers of High-Performance Polymer PTB7

et al. 2019

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A key characteristic of organic photovoltaic cells is the efficient charge separation in the active layer. Sufficient delocalization of the positive polaron in organic photovoltaic is considered essential for effective separation of the opposite charges and suppression of recombination. We use light-induced EPR and ENDOR spectroscopy combined with DFT calculations to determine the electronic structure of the positive polaron in PTB7-type oligomers. Utilizing the superior spectral resolution of high-frequency (130 GHz) D-band EPR, the principal components of the g-tensors were determined. Pulsed ENDOR spectroscopy at X-band allowed the measurement of 1 H hyperfine coupling constants. Comparison of g-tensors and 1 H hyperfine coupling constants of the PTB7-type oligomers with the high performance PTB7 polymer revealed a delocalization of the positive polaron in the polymer over about four monomeric units, corresponding to about 45 Å in length. Our current study thus not only determines the polaron delocalization length in PTB7, but also validates the approach combining EPR/ENDOR spectroscopy with DFT calculated magnetic resonance parameters. This is of importance in those cases where oligomers of defined length are not easily obtained. In addition, the delocalization of the neutral triplet exciton was also determined in the oligomers and compared with the polymer PTB7. The analysis revealed that the neutral triplet exciton is substantially more delocalized than the positive polaron, exceeding 10 monomeric units.

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CT Perfusion Techniques and Applications in Stroke and Cancer

Cited by 9 publications

References 56 publications

CT perfusion stroke lesion threshold calibration between deconvolution algorithms

CT perfusion stroke lesion threshold calibration between deconvolution algorithms

Blood–brain barrier permeability in survivors of immune-mediated thrombotic thrombocytopenic purpura: a pilot study

Polaron and Exciton Delocalization in Oligomers of High-Performance Polymer PTB7

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